docs: def _grammatical_join_filter(l, arg=None):
      """
      :param l: List of strings to join
      :param arg: A pipe-separated list of final_join (" and ") and
      initial_join (", ") strings. For example
      :return: A string that grammatically concatenates the items in the list.
      """
      if not arg:
          arg = " and |, "
      try:
          final_join, initial_joins = arg.split("|")
      except ValueError:
          final_join = arg
          initial_joins = ", "
      return grammatical_join(l, initial_joins, final_join)